I'd like to see a race through a power station with electrical pylons all over the place creating electrical currents that stream around the environment and conduct along the cars as they get close. Think something like the Death Star core - while the cars hammer around the central cylinder wall of a reactor, the core fusion reactor is streaming out plasma to the cars giving them a boost or messing with them, or just exploding cars off the wall (probably a bit to RNG for fair racing but meh, could be fun). Maybe if enough cars take out a core, it powers down a part of the track either forcing new roots or just messing with the lead of the race while the power boots back up letting those lagging behind a small amount of time to catch up. Style would be sleek metal look with cool lighting from electricity and plasma streams.
The Grave Yard
Track formed by junked machinery and vehicles making up the walls with weak stacks of crushed cars that can be smashed through forming short-cuts. Conveyor belts that can be raced on but sometimes rotate counter to the direction of the race to screw with handling and speed. Industrial robots dropping junkers on to the track causing explosions and crash hazards and ramp like surfaces. Maybe a molten area where the yard melt stuff down and crushers like those revolving spiked cylinders that mash stuff up could be hazards to jump over. Industrial/sewer piping forms walls and ceiling areas for inverted racing. Style and colours would be dark browns and molten reds/yellows with burning wrecks and lots of sparks at night.
Old abandoned city buried in post ice-age tundra. For this I'm just thinking of a high wind ice area where the snow and ice have formed massive angled spikes of ice that form natural curved surfaces to race on. Imagine a wind swept sand dune, but with ice forming over the lip of the dune. Then I had the idea to break it up with a city half buried with massive snow drifts making natural ramps up the sides of destroyed buildings with ice forming bridges across roof tops. Just thought it would look cool with massive ships sticking up out of the iced over ocean/harbour area to race on/through. Style would be harsh cold blue broken up with colour here and there from the objects buried.